Recent Korea Meteorological Administration forecasts and ensemble models from the European Centre for Medium-Range Weather Forecasts indicate Seoul's overnight low on May 21 will likely settle near 13–15°C under mostly clear skies and light northerly winds. This positioning aligns with late-May climatology, where historical records show average minima of 12–15°C amid spring warming and urban heat island moderation, though a La Niña transition favors slightly cooler conditions over Northeast Asia. Traders have priced the 13°C-or-below outcome highest because ongoing radiative cooling after recent drier periods could push temperatures lower than typical seasonal baselines, while any increase in cloud cover or southerly flow remains the main variable that might lift the minimum into the mid-teens. Updated model runs ahead of the date will clarify these thresholds.